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Old 12th November 2012, 07:32 AM   #31
Moonfly is offline Moonfly  Spain
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Hi MedPed.

Do you have any particular reason for choosing the drivers you have highlighted, if not, are we free to suggest drivers?

Running the behringer amp bridged in 4Ohms is the same load on the internals as 2 channels at 2 Ohms, so 2Ohms bridged isnt an option. Given the nature of the Behringer amps, I always suggest to massively over spec the amps for your needs. If you want 2KW, then simply buy an NU6000DSP. You can then rest in relative peace in the knowledge the amp is pretty much going to supply your required 2-3KW without any issues.

As for the 15 inch dual opposed idea. I would suggest perhaps looking at something like a pair of Fi Q15's, or SSD's for a cheaper option. They are sold as vehicle drivers but work in HT quite well as they have been designed to do that. Both drivers will work in 100 litre enclosures per pair of drivers. The Q's will take 3KW of power and the SSD 2KW. Both will comfortably hit over 100db in room at 15hz once eq'd.

In relation to using multiple drivers. Each driver has an optimal cabinet volume in which it will work. If you double the number of drivers, then you need to also double the cabinet volume to match, and so on and so on. On the point of coupling the drivers, it can only help. Being dual opposed, a pair of 15's will be fairly inert anyway, more so if you double your baffle thickness up, but you could if you wanted, run a threaded rod from one drivers mounting holes to the other, and clamp both drivers tight into the cabinet pulling against each other. This is something Kef do in their concept blade speakers with the bass drivers, and it certainly wont hurt.

Last edited by Moonfly; 12th November 2012 at 07:37 AM.
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Old 12th November 2012, 11:24 AM   #32
tvrgeek is offline tvrgeek  United States
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OP,

Let's get focused on a first speaker design. Don't get over exotic when you don't know what it will do for you.
A few basics:
Subs are OMNIDIRECTIONAL
Subs need large boxes
Subs need lots of power
Subs integrate best if as close to the mains as possible
Two separate subs will work far better than two drivers in one box.
The room is as important as the subs. A great sub won't fix room problems.
Sealed are far more forgiving than ported. I think they blend into the room better too.
Isobaric can halve the box size, but for a big price.
Car speakers are designed for cars, not housed. Differences trade-offs.
Almost all of the exotic coupling ideas, odd boxes and tricks here are not necessary to get a superb sub. The quality of the driver, correct size and sturdy box are most important. Leave the fancy stuff for after you have built a few.

So, first speaker. Have you played with any modeling tools like WinISD?
Do you understand T/S parameters and how to measure them?
Do you have the ability to measure the results, both in-room and out in a field?
Is this intended to be a one-time project, or are we going to ruin your life, suck you into the dark side and make a speaker DIY out of you?

Here are a couple of links that deacribe what I consider quite satisfactroy home music subs.
Critical Q Sub-Woofer
THOR - subwoofer
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Old 12th November 2012, 12:12 PM   #33
Moonfly is offline Moonfly  Spain
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Quote:
Originally Posted by tvrgeek View Post
OP,

Let's get focused on a first speaker design. Don't get over exotic when you don't know what it will do for you.

A few basics:
Subs are OMNIDIRECTIONA
They should be, and will be if they run cleanly and are setup properly.

Quote:
Originally Posted by tvrgeek View Post
Subs need large boxes
That statement has to be placed in proper perspective. There is a massive difference between the smallest sub, and the largest.

Quote:
Originally Posted by tvrgeek View Post
Subs need lots of power
Again, a huge difference between top and bottom tiers.

Subs integrate best if as close to the mains as possible[/QUOTE]

In theory, but its not always the case. A sub being some distance from the mains due to being dictated by other factors isnt a reason to expect the sub to respond badly. Seal subs naturally integrate better because of their design, as laid out by Linkwitz and Reilly.


Two separate subs will work far better than two drivers in one box.[/QUOTE]


Quote:
Originally Posted by tvrgeek View Post
The room is as important as the subs. A great sub won't fix room problems.
Agreed!

Sealed are far more forgiving than ported. I think they blend into the room better too.[/QUOTE]

This is true, again based on the research by Linkwitz and Reilly.

Car speakers are designed for cars, not housed. Differences trade-offs. [/QUOTE]

If this is in relation to the Fi suggestion. The SSD and Q series drivers were redesigned in 2010 so they could be used in a HT environment and work well. I have used them on many occasions and proved this to be true. Thats not to say they are the best or only option, but they do work and work quite well.
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Old 12th November 2012, 01:29 PM   #34
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Minor point:

Subs radiate omnidirectionally.

This does not mean that their source can not be determined by a listener. This is something that seems to have gotten confused by an awful lot of people.

_-_-bear
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Old 12th November 2012, 01:43 PM   #35
Moonfly is offline Moonfly  Spain
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Join Date: Oct 2012
Quote:
Originally Posted by tvrgeek View Post
OP,

Let's get focused on a first speaker design. Don't get over exotic when you don't know what it will do for you.

A few basics:
Subs are OMNIDIRECTIONA
They should be, and will be if they run cleanly and are setup properly.

Quote:
Originally Posted by tvrgeek View Post
Subs need large boxes
That statement has to be placed in proper perspective. There is a massive difference between the smallest sub, and the largest.

Quote:
Originally Posted by tvrgeek View Post
Subs need lots of power
Again, a huge difference between top and bottom tiers.

Quote:
Originally Posted by tvrgeek View Post
Subs integrate best if as close to the mains as possible
In theory, but its not always the case. A sub being some distance from the mains due to being dictated by other factors isnt a reason to expect the sub to respond badly. Seal subs naturally integrate better because of their design, as laid out by Linkwitz and Reilly.


Quote:
Originally Posted by tvrgeek View Post
Two separate subs will work far better than two drivers in one box.

Quote:
Originally Posted by tvrgeek View Post
The room is as important as the subs. A great sub won't fix room problems.
Agreed!

Quote:
Originally Posted by tvrgeek View Post
Sealed are far more forgiving than ported. I think they blend into the room better too.
This is true, again based on the research by Linkwitz and Reilly.

Quote:
Originally Posted by tvrgeek View Post
Car speakers are designed for cars, not housed. Differences trade-offs.
If this is in relation to the Fi suggestion. The SSD and Q series drivers were redesigned in 2010 so they could be used in a HT environment and work well. I have used them on many occasions and proved this to be true. Thats not to say they are the best or only option, but they do work and work quite well.
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Old 12th November 2012, 02:07 PM   #36
tb46 is offline tb46  United States
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Default Wait, there is more.......

Hi MedPed,

I must have skipped this before, Post #1: "...I might consider a folded horn design that is vertical, and folds over only once..."

Well, you're in luck again: Lab12 - Tapped Horn - - in Post #188 is the updated drawing for a single fold tappe horn using the Eminence LAB12 Eminence LAB 12 Professional 12" Subwoofer Speaker 290-570.

This has been build successfully numerous times in the double fold version (which is the main part of that thread). From playing around with the simulation I'm convinced that this would work at least as well.

You could build a proof of concept from two sheets of MDF and a single driver for less than $300.--, and it's an easy build.

Put that one into your favorite spot, and than you have all the time you want to ponder the rest of the subwoofer world.

Regards,
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Old 12th November 2012, 02:38 PM   #37
sreten is offline sreten  United Kingdom
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Hi,

If you want to go very low generally speaking vented is the way to go.

Take typical high quality / value driver designed to
go low, a good example is the Eminence LAB12 :

http://www.eminence.com/pdf/LAB_12.pdf

A typical application is a 100L cabinet tuned to 20Hz.

This will be essentially flat down to 20Hz in room, -3dB@25Hz,
(and go down to approximately 16Hz or so in room).

A sealed version is typically 50L, but is -9dB@25Hz. A sub amplifier
with an inbuilt bass boost of 6dB @ 25Hz will restore the response.

But the latter will need a 4 times as powerful amplifier to reach
maximum levels. Not only that, an effective port will act like
4 drivers at the port frequency, giving much higher max SPL,
so in the end the same amplifier will suit both cases.

Comparing the two cases again vented is -6dB@20Hz, sealed -13dB@20Hz.

Sealed is -16.5dB @16Hz, and retuning the vented to 18Hz its -10dB@16Hz.
10dB is about the maximum room gain you can expect, sealed needs some EQ.

The point of all this is you can go sealed + EQ but you take a bit hit
in maximum SPL around the port frequency. With one driver adding
a port doubles the size of the box, but is goes as loud as 4 sealed
boxes (i.e. its half the size) in the low bass around the port tuning.

As ever the compromise is quality versus quantity, but on a driver cost
versus performance perspective, vented wipes the floor with using sealed.

http://www.bkelec.com/HiFi/Sub_Woofe...h%20Review.pdf

And the latest version :

Monolith-DF

A friend has the latest one, it sounds very good, his valve system
though hardly pushes its SPL capabilities, in that respect its not
and ideal match to his system.

Defined goals regarding wanted bass extension and SPL capability
would be good. What you think you need might not be right.

Also tall TL's can deliver very good low bass in a small footprint,
with very similar advantages to vented around the line tuning.

rgds, sreten.

Vibration cancellation is simplest done with two drivers on opposite faces.
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Old 12th November 2012, 09:31 PM   #38
tvrgeek is offline tvrgeek  United States
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Quote:
Originally Posted by bear View Post
Minor point:

Subs radiate omnidirectionally.

This does not mean that their source can not be determined by a listener. This is something that seems to have gotten confused by an awful lot of people.

_-_-bear
How true. Localization is mostly a function of crossover frequency and slope. I am a fan of 65 Hz 4th order to prevent localization. High harmonic distortion can cause some localization, but only a few are that bad. The closer the subs are to the mains, the less the localization. ( The THX 80 Hz 3rd is fine if the subs are used for speaker stands) 65 is a handy number as it is a good number for a 5 to 7 inch two way.

I point out the omni-radiation as there are even more misunderstood ideas about multi-facing, bi-polar, dipolar and other solutions looking for a problem.

Now, when I say close to the mains to integrate well, the real important ting is that if the distance from the subs to the mains is the same, you will have far less issues with additive or subtractive response variations. One ic the center is not bad. The worst thing to do is put one in the corner where is ti a different distance to each main. The steeper the crossover, the slightly less this is a problem. Go measure it if you have not.

Car subs are typically designed to only got to 50 or 60, but at very high levels and in very small boxes. Not all, but most.

As simple as a sub looks, it is still pretty complex to understand. This is why I suggest one start with something very basic. Learn all about it and then make decisions on what to try next. If it really was that easy, we could just say "do it this way" . As there are still as many different versions and ideas as DIY-ers then it should be clear it is not that simple.

I believe WinISL will run fine on the Mac with a Windows emulator. I am sure there are other Mac specific tools that do the same. I think there are even iPhone apps.

For any newbe, I recommend doing some reading. Joe D'Appolito Measuring Loudspeakers is a very good reference. A lot of good stuff on places like True Audio, Zaph, or Linkwatz.
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Old 13th November 2012, 01:42 AM   #39
MedPed is offline MedPed  United States
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Thanks so much guys for all the input.

Regarding the choice of drivers, I am not hung up on the the TC Sounds. I looked them up in response to the suggestion of the Epics.

About the behringer, I too am suspicious of the quoted numbers. Even if it is 80-90% efficient, it would have to have a heck of lot of capacitance to support those numbers, which I doubt, but it seems to be fairly popular for a reason and am sure it makes for a good sub amp. That along with all suggested alternatives will always be considered.

About winisd. Currently I don't have windows on my mac, but will play with it after hours on my work PC.

Regarding sealed vs ported. I get that the ported will go lower, but how low are we talking. If I am only interested in some output at 15 Hz, but otherwise fairly linear up to 20 Hz, do I still need to go ported? Sealed has the advantage of generally requiring smaller cabinet space (or so I understand), and also have the reputation of being more musically accurate and quicker.

As far as understanding and measuring stuff. I do not quite understand T/S nor do I have the capabilities to measure them, or output. I have begun reading, and hopefully will grasp at least half of it. Thanks for links to the reference materials.

About the single fold tap horn, thanks for that link, I read the last few pages of the thread, and it seems quite interesting. A few questions about that - will it be a relatively simple project for a newbie, without any fancy measuring equipment, or should I stick to the idea of sealed subs - either dual opposed or single cabinets. Secondly, what do they sound like. I.e. the "house sound" of tapped horns. Do they have a certain characteristic to their sounds that I should consider before I consider the project.

Regarding one time project or not... Safe to say, I am being sucked to the dark side of DIY. I have always enjoyed screwing around with stuff, and have always had a passion for music. So I am probably in for the long haul. Feel sorry for you guys - you may be stuck with me for ever "evil laugh". In that same vein, is there some "basic DIY survival kit" that I should be looking at acquiring. That would be an awesome other post - or publication, recommendations for equipment for newbies.

In summary:
No set design, drivers, or amp selection as yet. Goal frequency response is 20-80Hz. Rooms size is approx 16x20x9 feet. Even split with movies and music. Moderate to high listening levels - extreme only for the 1-2/year parties which will be music only without movies so extension not important for those days.

My initial inclination was that of sealed cabinet with dual opposed drivers, but am willing to entertain just any design as long as it's size is acceptable. The more I think of it, I might be able to get away with two single sealed or ported subwoofers - one beneath each of my bookshelf that I use as my mains, and I do not necessarily have to make it look like an end table, or stick a tall horn in the corner. Part of me is hung on the idea that the dual opposed will make for a better sounding sub, but the general consensus I seem to feel on this thread is that, this being my first sub, it will likely have enough shortcomings, that the teeny bit of distortion I will try and reduce with dual opposed will be **** in the ocean - and therefore I am will dump that thought.

... back to the drawing board. But with more knowledge, but no decisions. The road to peace is full of confusion! I am quite excited about this!

BTW the speakers I will be running these with will be Emotiva Pro Airmotiv 6 powered monitors. I love them. Folded ribbon tweeters, and 6.5 mid/woofer powered by dual amps - 100W each for the tweeters, and 110W each for the woofers.
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Old 13th November 2012, 03:48 AM   #40
tb46 is offline tb46  United States
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Default Post #39

Hi MedPed,

"...the single fold tap horn...will it be a relatively simple project... Do they have a certain characteristic to their sounds that I should consider..."

I would consider it a simple entry-level project. In this simple form it's one more board than a sealed box, what could go wrong :-).

The only "must have test equipment" is something like a Radio Shack SPL meter. You'll need that for any subwoofer project during the integration phase anyway, and it would make it easy to find out at what levels you are usually listening, and what levels you never want to get to.

This single fold TH is not designed to go below 20Hz, but will get to 20Hz with some authority. As with any ported (vented) box it will need a high-pass filter to prevent excessive cone movement below the point where the cabinet unloads.

As to what a sub sounds like (OK I can hear the knifes being sharpened in the background): after applying the correct filters to a properly designed sub used within its normal output range there should not be as great a difference to other similarly well designed and applied subs as people seem to make it sound. The big advantage of a tapped horn over the sealed box is the total dynamic range, the lower compression at high output levels, the lower power required to reach a given SPL (take a look at the attached graph), but if you ever use that range/level, that's the question. It sure is nice to have some dynamic reserve though. In general people seem to like the effortlessness of the tapped horn when handling large dynamic changes. There are conflicting reports as to the need for delay (for the main speaker signal) something to try. Take a look at Erik's (Volvotreter) web site for more information: Tapped Horns .

I'll attach a quick graph comparing the LAB12 driver in the single fold tapped horn (TH) and a V_net=75L sealed box (SB). Both driven w/ 125W into 6_Ohm, which brings the peak excursion to ~~Xmax (which is the safe limit that should not be exceeded; Xmech or Xlim is the mechanical limit the exceeding of which will likely lead to driver damage).

"...subwoofers - one beneath each of my bookshelf that I use as my mains..."

As your mains seem to be somewhat limited in their low end this approach would probably work. See: filters, phasing, level matching, multiple amplifier...all kinds of ways to get from here to there, all easier with sealed boxes. OK, now we have two sealed boxes for the range extension of your mains, and a TH to add some oomph (technical term). 2 ea. JBL GTO1214 SB (budget) and 1 ea. LAB12 TH.

"...this being my first sub, it will likely have enough shortcomings..."

Not necessarily.

Best of luck,
Attached Images
File Type: jpg TH_v_SB_SPL.jpg (77.8 KB, 80 views)
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Last edited by tb46; 13th November 2012 at 03:51 AM.
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